An electrical N.times.1 selector switch is an N.times.1 switching device which routes any one of the N input lines to the single output port, as shown in FIG. 1. An optical N.times.1 selector switch is the optical analog of the electrical N.times.1 selector switch where the input and output ports are optical fibers carrying one or more optical communication signals at different wavelengths. Certain selector switches may permit selection of more than one input port and adding (under certain rules) the signals from the selected ports. This properly is called the collection capability of the selector switch.
Prior known selectors employed mechanical switching elements. Such prior arrangements employing mechanical selectors were limited in selecting only one line at a time, their speed was slow, and their reliability was less than desirable. One such arrangement is shown in FIG. 1 where a plurality of incoming optical lines 100-1 through 100-N which are supplied to the selector 101 and switching element 103. Switching element 103, under control of actuator 102, then would select one of the optical lines 100 to be supplied to output optical line 104.
A number of electro-mechanical optical selector switches are presently available. These devices are based on mechanically moving the input and/or output fibers or utilizing various reflective or deflective optical elements to align beams of light out of the input fibers and routing them to the output fiber. Clearly, these mechanical switches are slow and, in most cases, do not permit collection capability, a desirable feature in communication systems. In some cases, the optical loss associated with these elements is significant.
Solid state wave-guide selector switches based on lithium niobate (see for example U.S. Pat. No. 5,181,134) or indium phosphide optical switching devices are also available which solve the speed problems. The drawback involved with these optical switching devices include polarization dependence and significant optical losses. The large optical insertion losses connected with these devices soon become intolerable when such devices are concatenated.